Methods of depth based block partitioning

ABSTRACT

A method of simplified depth-based block partitioning (DBBP) for three-dimensional and multi-view video coding is disclosed. In one embodiment, the method receives input data associated with a current texture block in a dependent view, and determines a corresponding depth block or a reference texture block in a reference view for the current texture block. Then, the method derives a representative value based on the corresponding depth block or the reference texture block, and generates a current segmentation mask from the corresponding depth block or the reference texture block. Then, the method selects a current block partition from block partition candidates, wherein the representative value is used for generating the segmentation mask or selecting the current block partition or both, and applies DBBP coding to the current texture block according to the current segmentation mask generated and the current block partition selected.

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention is a Continuation of U.S. patent application Ser.No. 14/583,628, filed on Dec. 27, 2014, now U.S. Pat. No. 9,992,494,which claims priority to PCT Patent Application, Ser. No.PCT/CN2014/072194, filed on Feb. 18, 2014, entitled “Methods forDepth-based Block Partitioning”. The PCT Patent Application is herebyincorporated by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to three-dimensional (3D) and multi-viewvideo coding. In particular, the present invention relates to texturecoding utilizing depth-based block partitioning (DBBP) to improve codingefficiency.

BACKGROUND AND RELATED ART

Three-dimensional (3D) television has been a technology trend in recentyears that intends to bring viewers sensational viewing experience.Various technologies have been developed to enable 3D viewing. Amongthem, the multi-view video is a key technology for 3DTV applicationamong others. The traditional video is a two-dimensional (2D) mediumthat only provides viewers a single view of a scene from the perspectiveof the camera. However, the 3D video is capable of offering arbitraryviewpoints of dynamic scenes and provides viewers the sensation ofrealism.

The 3D video is typically created by capturing a scene using videocamera with an associated device to capture depth information or usingmultiple cameras simultaneously, where the multiple cameras are properlylocated so that each camera captures the scene from one viewpoint. Thetexture data and the depth data corresponding to a scene usually exhibitsubstantial correlation. Therefore, the depth information can be used toimprove coding efficiency or reduce processing complexity for texturedata, and vice versa. For example, the corresponding depth block of atexture block reveals similar information corresponding to the pixellevel object segmentation. Therefore, the depth information can help torealize pixel-level segment-based motion compensation. Accordingly, adepth-based block partitioning (DBBP) has been adopted for texture videocoding in the current 3D-HEVC (3D video coding based on the HighEfficiency Video Coding (HEVC) standard).

The current depth-based block partitioning (DBBP) comprises steps ofvirtual depth derivation, block segmentation, block partition, andbi-segment compensation. First, virtual depth is derived for the currenttexture block using a disparity vector from neighboring blocks (NBDV).The derived disparity vector (DV) is used to locate a depth block in areference view from the location of the current texture block. Thereference view may be a base view. The located depth block in thereference view is then used as a virtual depth block for coding thecurrent texture block. The virtual depth block is to derive blocksegmentation for the collocated texture block, where the blocksegmentation can be non-rectangular. A mean value, of the virtual depthblock is determined. A binary segmentation mask is generated for eachpixel of the block by comparing the virtual depth value with the meanvalue, d. The mean value is utilized to compare with each virtual depthvalue to generate the mask values. If the left-up corner virtual depthvalue is larger than the mean value, all segmentation mask valuescorresponding to the depth values larger than d are 0; and all thesegmentation mask values corresponding to the depth values less than dare 1. FIGS. 1A-B illustrates an example of block segmentation based onthe virtual block. In FIG. 1A, corresponding depth block 120 in areference view for current texture block 110 in a dependent view islocated based on the location of the current texture block and derivedDV 112, which is derived using NBDV according to 3D-HEVC. The mean valueof the virtual block is determined in step 140. The values of virtualdepth samples are compared to the mean depth value in step 150 togenerate segmentation mask 160. The segmentation mask is represented inbinary data to indicate whether an underlying pixel belongs to segment 1or segment 2, as indicated by two different line patterns in FIG. 1B.

In order to avoid high computational complexity associated withpixel-based motion compensation, DBBP uses block-based motioncompensation. Each texture block may use one of 6 non-square partitionsconsisting of 2N×N, N×2N, 2N×nU, 2N×nD, nL×2N and nR×2N, where thelatter four block partitions correspond to AMP (asymmetric motionpartition). After a block partition is selected from theseblock-partition candidates by block partition selection process, twopredictive motion vectors (PMVs) are derived for the partitioned blocksrespectively. The PMVs are then utilized for compensating theto-be-divided two segments. According to the current 3D-HEVC, the bestblock partition is selected by comparing the segmentation mask and thenegation of the segmentation mask (i.e., the inverted segmentation mask)with the 6 non-square partition candidates (i.e., 2N×N, N×2N, 2N×nU,2N×nD, nL×2N and nR×2N). The pixel-by-pixel comparison counts the numberof so-called matched pixels between the segmentation masks and the blockpartition patterns. There are 12 sets of matched pixels need to becounted, which correspond to the combinations of 2 complementarysegmentation masks and 6 block partition types. The block partitionprocess selects the candidate having the largest number of matchedpixels. FIG. 2 illustrates an example of block partition selectionprocess. In FIG. 2, the 6 non-square block partition types aresuperposed on top of the segmentation mask and the correspondinginverted segmentation mask. A best matching partition between a blockpartition type and a segmentation mask is selected as the blockpartition for the DBBP process.

After a block partition type is selected, two predictive motion vectorscan be determined. Each of the two predictive motion vectors is appliedto the whole block to form a corresponding prediction block. The twoprediction blocks are then merged into one on a pixel by pixel basisaccording to the segmentation mask and this process is referred asbi-segment compensation. FIG. 3 illustrates an example of DBBP process.In this example, the N×2N block partition type is selected and twocorresponding motion vectors (MV1 and MV2) are derived for twopartitioned blocks respectively. Each of the motion vectors is used tocompensate a whole texture block (310). Accordingly, motion vector MV1is applied to texture block 320 to generate prediction block 330according to motion vector MV1, and motion vector MV2 is applied totexture block 320 also to generate prediction block 332 according tomotion vector MV2. The two prediction blocks are merged by applyingrespective segmentation masks (340 and 342) to generate the finalprediction block (350).

While the DBBP process reduces computational complexity by avoidingpixel-by-pixel based motion compensation, problems still exist in thesteps of block partition and block segmentation. One issue is associatedwith the mean value calculation for block partition and blocksegmentation. The steps utilize different mean value calculations forblock partition and block segment. For block partition, the mean valueis determined based on the average of all the upper-left corner pixelsof the 4×4 sub-blocks in the corresponding depth block. On the otherhand, for block segmentation, the mean value is determined according tothe average of all pixels of the corresponding depth block. The twodifferent mean value calculations in DBBP will inevitably increase theencoding and decoding complexity. Another issue is associated with thehigh computational complexity involved in the block partitionprocessing. However, this step is only utilized to derive suitablemotion vectors from more reliable block partitioning. The blockpartition type doesn't play any role in generating the final predictionblock after the motion vectors are derived as evidenced in FIG. 3. Afurther issue associated with the block partitioning is the large numberof partition types due to the use of AMP. The current practicedetermines whether to utilize AMP partitions directly based on the CUsize. The use of AMP may not necessarily provide noticeable improvementin system performance. Therefore, it is desirable to develop means toovercome these issues mentioned here.

BRIEF SUMMARY OF THE INVENTION

A method of simplified depth-based block partitioning (DBBP) forthree-dimensional and multi-view video coding is disclosed. In oneembodiment, the derivation of a representative value of a correspondingdepth block or a reference texture block in a reference view forgenerating a segmentation mask and selecting a block partition areunified. This unified representative value derivation can reduce therequired computations compared to the conventional DBBP coding. Theunified representative value may correspond to the mean, the average orthe sum of all samples or partial samples of the corresponding depthblock or the reference texture block. Said deriving the unifiedrepresentative value can be performed during said generating the currentsegmentation mask and information regarding the unified representativevalue is then provided to said selecting the current block partition, orvice versa.

Selecting the current block partition may comprise comparing selectedsamples at multiple fixed positions in the corresponding depth block orthe reference texture block. The multiple fixed positions may correspondto upper-left, upper-right, lower-left and lower-right corner samples ofthe corresponding depth block or the reference texture block. Themultiple fixed positions may also correspond to upper-left, upper-right,lower-left and lower-right corner samples of each partitioned block ofeach block partition candidate corresponding to the corresponding depthblock or the reference texture block. The unified representative valuemay also be calculated as an average of selected samples correspondingto sub-sampled positions of the corresponding depth block or thereference texture block. In this case, the unified representative valueis calculated for each partitioned block of each block partitioncandidate corresponding to the corresponding depth block or thereference texture block. The unified representative value may also becalculated from an average of all samples in the corresponding depthblock or the reference texture block. Selecting the current blockpartition from block partition candidates may also comprise determiningabsolute difference between a first sum of first samples of a firstpartitioned block and a second sum of second samples of a secondpartitioned block for each block partition candidate, and selecting theblock partition candidate having a largest absolute difference as thecurrent block partition.

One or more flags in a video bitstream may be used to indicate availableblock partition candidates used for selecting the current blockpartition. Furthermore, another one or more flags may be used toindicate the block partition candidate selected as the current blockpartition. One or more flags in the video bitstream may also be used toindicate a partition direction of the block partition candidate selectedas the current block partition. The block partition candidates mayexclude AMP (asymmetric motion partitions) when AMP is not available fora current picture, current slice or current coding unit containing thecurrent block.

In another embodiment, the first representative value, the secondrepresentative value, or both are calculated from partial samples of thecorresponding depth block or the reference texture block. The partialsamples may correspond to four corner samples of the corresponding depthblock or the reference texture block, and the current texture blockcorresponds to a CTU (coding tree unit), a CTB (coding tree block), a CU(coding unit), or a PU (prediction unit).

In yet another embodiment, the first representative value is determinedfrom four corner samples of the corresponding depth block or thereference texture block and the second representative value isdetermined for each partitioned block of a block partition candidatecorresponding to the corresponding depth block or the reference textureblock based on four corner samples of each partitioned block.

In yet another embodiment, a first representative value for firstsamples in a first partitioned block of the corresponding depth block orthe reference texture block, and a second representative value forsecond samples in a second partitioned block of the corresponding depthblock or the reference texture block for each of block partitioncandidates are determined. The current block partition is selected basedon one of the block partition candidates that has a largest absolutedifference between the first representative value and the secondrepresentative value.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an exemplary derivation process to derive acorresponding depth block in a reference view for a current textureblock in a dependent view.

FIG. 1B illustrates an exemplary derivation process to generate thesegmentation mask based on the corresponding depth block in a referenceview for a current texture block in a dependent view.

FIG. 2 illustrates an example of 12 possible combinations of blockpartition types and segmentation mask/inverted segmentation mask forblock partition selection.

FIG. 3 illustrates an exemplary processing flow for 3D or multi-viewcoding using depth-based block partitioning (DBBP).

FIG. 4 illustrates an example of representative value derivation basedon four corner samples of the corresponding depth block in a referenceview.

FIG. 5 illustrates an example of representative value derivation foreach partitioned block of a block partition candidate based on fourcorner samples of the partitioned block.

FIG. 6 illustrates a flowchart of an exemplary system incorporating anembodiment of the present invention to simplify depth-based blockpartitioning (DBBP), where the representative value of the correspondingdepth block or the reference texture block is unified for generating asegmentation mask and selecting a block partition for DBBP.

FIG. 7 illustrates a flowchart of an exemplary system incorporating anembodiment of the present invention to simplify depth-based blockpartitioning (DBBP), where the representative value derivation is basedon partial samples for generating the segmentation mask, selecting ablock partition or both.

FIG. 8 illustrates a flowchart of an exemplary system incorporating anembodiment of the present invention to simplify depth-based blockpartitioning (DBBP), where the representative value for generating asegmentation mask is based on four corner samples of the correspondingdepth block or the reference texture block, and the representative valuefor selecting a block partition is derived based on four corner samplesof respective partitioned blocks of a block partition candidate.

FIG. 9 illustrates a flowchart of an exemplary system incorporating anembodiment of the present invention to simplify depth-based blockpartitioning (DBBP), where a block partition is selected according tothe largest absolute difference between the two sums corresponding totwo partitioned blocks of a block partition candidate.

DETAILED DESCRIPTION OF THE INVENTION

In order to overcome the computational complexity issues associated withexisting depth-based block partitioning (DBBP) process, the presentinvention discloses various embodiments to reduce the complexity.

In one embodiment, the mean value calculations for selecting a blockpartition and generating a segmentation mask for DBBP are unified. Inother words, the same mean value calculation is used for both the blockpartition process and the block segmentation process.

According to this embodiment, the block segmentation utilizes an inputparameter provided from the block partition process. This inputparameter can be the averaged value from all depth samples in thecorresponding depth block, the averaged value of all upper-left cornerpixels of k×k sub-blocks of the corresponding depth block, where k is aninteger such as k=4 is. Other means to derive the mean value may also beused. For example, the upper-left corner pixels can be replaced by theupper-right, lower-left, or lower-right pixels. Since informationassociated with the mean value is provided from the block partitionprocess, there is no need for the block segmentation process tocalculate the mean value again. Alternatively, the informationassociated with the mean value can be determined by the blocksegmentation process and provided to the block partition process.

The mean value for the corresponding depth block or a partitioned blockof the corresponding depth block may be determined from the average ofall upper-left corner pixels of k×k sub-blocks of the correspondingdepth block. In this case, the mean value derived using sub-sampled datarepresents an approximation to the actual mean of the correspondingdepth block. For generality, the value derived for each block orpartitioned block for block partition or block segmentation is referredas a “representative value” in this disclosure. Furthermore, therepresentative value of a block or partitioned block for block partitionor block segmentation does not have to be the averaged value of selectedsamples. The representative value may correspond to a mean, an averageor a sum of all samples or partial samples of the corresponding depthblock according to the present invention.

In another embodiment, the complexity associated with the mean valuecalculation is substantially reduced by deriving the representativevalue based on a small set of depth sample locations (i.e., partialsamples of a block). For example, instead of using all depth samples orthe upper-left corner samples of k×k sub-blocks in the derived depthblock, only four corner samples of respective block are used fordetermining the representative value. For example, during the blocksegmentation process, the mean value of the derived depth blockcorresponding to a coding unit (CU) has to be calculated. The partialsamples may correspond to four corner samples of the corresponding depthblock as shown in FIG. 4. The current texture block may correspond to aCTU (coding tree unit), a CTB (coding tree block), a CU (coding unit),or a PU (prediction unit), where CTU, CTB, PU and CU are various picturedata structure as described in the High Efficiency Video Coding (HEVC)standard. For block partition process, the representative value of eachrespective partitioned block (i.e., a prediction unit (PU)) of a blockpartition candidate can also be derived based on 4 corner samples of therespective PU as shown in FIG. 5.

In another embodiment, the complexity associated with block partitioningis substantially reduced by comparing pixels at pre-defined locations ofthe corresponding depth block for each partition candidate. According tothis embodiment, the block partition process is simplified by comparingthe relationships among the pixels at pre-defined locations of thecorresponding depth block for each block partition candidate. Accordingto this embodiment, m pixels at pre-defined locations of the deriveddepth block for each partitioned block of a block partition candidateare used to determine the desired block partition. For example, m can beset to be equal to 4 and the positions of the 4 pixels correspond to the4 corner locations of each partitioned block of a block partitioncandidate associated with the corresponding depth block, as shown inFIG. 5. For a block partition candidate p, let S1 _(p) and S2 _(p) bethe sums of the 4 corner pixels in the first and the second partitionedblocks, M_(p) be the absolute difference between S1 _(p) and S2 _(p).According to an embodiment of the present invention, the block partitionis selected according to the block partition candidate p having thelargest absolute difference, M_(p). While the sums, S1 _(p) and S2 _(p)are used as “representative values” for individual partition blocks,other representative values may also be used. For example, the averageof the 4 corner samples can be used, which will result in the same blockpartition decision as the sum.

The inclusion of AMP in the block partition candidates will causeincreased complexity for block partition decision. In yet anotherembodiment of the present invention, AMP partitions are included ascandidates only if the current CU size is larger than 8×8 and AMPpartitions is enabled for the current CU. Furthermore, different blockpartition candidates may be used. In this case, one or more syntaxelements (e.g., flags) may be signaled in the bitstream to indicate theavailable block partition candidates. In order for a decoder to recoverthe block partition selected at the encoder end, one or more syntaxelements (e.g., flags) may be signaled in the bitstream to indicate theblock partition selected. (modify flag in spec)

While the derived depth block is used to generate a segmentation mask, areference texture block in a reference view may also be used for DBBP.In this case, the reference texture block in a reference view is locatedand used for the DBBP process as if it were a corresponding depth block.In this case, the representative value is derived based on the referencetexture block. The segmentation mask is derived based on the referencetexture block. The embodiments disclosed above using the correspondingdepth block in a reference view are applicable to the case using thereference texture block in a reference view.

FIG. 6 illustrates a flowchart of an exemplary system incorporating anembodiment of the present invention to simplify depth-based blockpartitioning (DBBP), where the representative value of the correspondingdepth block or the reference texture block is unified. The systemreceives input data associated with a current block in a dependent viewas shown in step 610. For encoding, the input data corresponds to pixeldata to be encoded. For decoding, the input data corresponds to codedpixel data to be decoded. The input data may be retrieved from memory(e.g., computer memory, buffer (RAM or DRAM) or other media) or from aprocessor. A corresponding depth block or a reference texture block in areference view for the current texture block is determined in step 620.A unified representative value is derived based on the correspondingdepth block or the reference texture block in step 630. A currentsegmentation mask is generated from the corresponding depth block or thereference texture block using the unified representative value in step640. A current block partition is selected from block partitioncandidates based on the corresponding depth block or the referencetexture block and the unified representative value in step 650. DBBPcoding is then applied to the current texture block according to thecurrent segmentation mask generated and the current block partitionselected in step 660.

FIG. 7 illustrates a flowchart of an exemplary system incorporating anembodiment of the present invention to simplify depth-based blockpartitioning (DBBP), where the representative value derivation is basedon four corner samples for generating the segmentation, selecting ablock partition or both. The system receives input data associated witha current block in a dependent view as shown in step 710. Acorresponding depth block or a reference texture block in a referenceview for the current texture block is determined in step 720. A currentsegmentation mask is generated from the corresponding depth block or thereference texture block using a first representative value of thecorresponding depth block or the reference texture block in step 730. Acurrent block partition is selected from block partition candidatesbased on the corresponding depth block or the reference texture blockand a second representative value of the corresponding depth block orthe reference texture block in step 740. DBBP coding is then applied tothe current texture block according to the current segmentation maskgenerated and the current block partition selected in step 750, wherethe first representative value, the second representative value, or bothare calculated from partial samples of the corresponding depth block orthe reference texture block.

FIG. 8 illustrates a flowchart of an exemplary system incorporating anembodiment of the present invention to simplify depth-based blockpartitioning (DBBP), where the representative value for generating blocksegmentation mask is based on four corner samples of the correspondingdepth block or the reference texture block, and the representative valuefor selecting the block partition is derived based on four cornersamples of respective partitioned blocks of a block partition candidate.The system receives input data associated with a current block in adependent view as shown in step 810. A corresponding depth block or areference texture block in a reference view for the current textureblock is determined in step 820. A first representative value isdetermined from first four corner samples of the corresponding depthblock or the reference texture block in step 830. A current segmentationmask is generated from the corresponding depth block or the referencetexture block using the first representative value in step 840. A secondrepresentative value for each partitioned block of a block partitioncandidate corresponding to the corresponding depth block or thereference texture block is determined based on second four cornersamples of said each partitioned block in step 850. A current blockpartition is selected from block partition candidates based on thecorresponding depth block or the reference texture block and the secondrepresentative values associated with the block partition candidates instep 860. DBBP coding is then applied to the current texture blockaccording to the current segmentation mask generated and the currentblock partition selected in step 870.

FIG. 9 illustrates a flowchart of an exemplary system incorporating anembodiment of the present invention to simplify depth-based blockpartitioning (DBBP), where the block partition is selected according tothe largest absolute difference between the two sums corresponding totwo partitioned blocks. The system receives input data associated with acurrent block in a dependent view as shown in step 910. A correspondingdepth block or a reference texture block in a reference view for thecurrent texture block is determined in step 920. A current segmentationmask is generated from the corresponding depth block or the referencetexture block in step 930. A first representative vale for first samplesin a first partitioned block of the corresponding depth block or thereference texture block, and a second representative vale for secondsamples in a second partitioned block of the corresponding depth blockor the reference texture block are determined for each of blockpartition candidates in step 940. A current block partition is selectedbased on one of the block partition candidates that has a largestabsolute difference between the first representative vale and the secondrepresentative value in step 950. DBBP coding is then applied to thecurrent texture block according to the current segmentation maskgenerated and the current block partition selected in step 960.

The flowcharts shown above are intended to illustrate examples ofsimplified depth-based block partitioning (DBBP) according to thepresent invention. A person skilled in the art may modify each step,re-arranges the steps, split a step, or combine steps to practice thepresent invention without departing from the spirit of the presentinvention.

The above description is presented to enable a person of ordinary skillin the art to practice the present invention as provided in the contextof a particular application and its requirement. Various modificationsto the described embodiments will be apparent to those with skill in theart, and the general principles defined herein may be applied to otherembodiments. Therefore, the present invention is not intended to belimited to the particular embodiments shown and described, but is to beaccorded the widest scope consistent with the principles and novelfeatures herein disclosed. In the above detailed description, variousspecific details are illustrated in order to provide a thoroughunderstanding of the present invention. Nevertheless, it will beunderstood by those skilled in the art that the present invention may bepracticed.

Embodiment of the present invention as described above may beimplemented in various hardware, software codes, or a combination ofboth. For example, an embodiment of the present invention can be acircuit integrated into a video compression chip or program codeintegrated into video compression software to perform the processingdescribed herein. An embodiment of the present invention may also beprogram code to be executed on a Digital Signal Processor (DSP) toperform the processing described herein. The invention may also involvea number of functions to be performed by a computer processor, a digitalsignal processor, a microprocessor, or field programmable gate array(FPGA). These processors can be configured to perform particular tasksaccording to the invention, by executing machine-readable software codeor firmware code that defines the particular methods embodied by theinvention. The software code or firmware code may be developed indifferent programming languages and different formats or styles. Thesoftware code may also be compiled for different target platforms.However, different code formats, styles and languages of software codesand other means of configuring code to perform the tasks in accordancewith the invention will not depart from the spirit and scope of theinvention.

The invention may be embodied in other specific forms without departingfrom its spirit or essential characteristics. The described examples areto be considered in all respects only as illustrative and notrestrictive. The scope of the invention is therefore, indicated by theappended claims rather than by the foregoing description. All changeswhich come within the meaning and range of equivalency of the claims areto be embraced within their scope.

The invention claimed is:
 1. A method of depth-based block partitioning(DBBP) for multi-view video coding or three-dimensional (3D) videocoding, the method comprising: receiving input data associated with acurrent texture block in a dependent view; determining a correspondingdepth block or a reference texture block in a reference view for thecurrent texture block; deriving a representative value based on thecorresponding depth block or the reference texture block; generating acurrent segmentation mask from the corresponding depth block or thereference texture block; selecting a current block partition from blockpartition candidates, wherein the representative value is used forgenerating the segmentation mask or selecting the current blockpartition or both; and applying DBBP coding to the current texture blockaccording to the current segmentation mask generated and the currentblock partition selected, wherein the representative value is calculatedfrom partial samples of the corresponding depth block or the referencetexture block, and the partial samples correspond to only four cornersamples of the corresponding depth or the reference texture block, andthe texture block corresponds to a coding tree unit (CTU), a coding treeblock (CTB), a coding unit (CU), or a prediction unit (PU).
 2. Themethod of claim 1, wherein the representative value corresponds to anaverage or a sum of the partial samples of the corresponding depth blockor the reference texture block.
 3. The method of claim 1, wherein saidderiving the representative value is performed during said generatingthe current segmentation mask.
 4. The method of claim 1, furthercomprising signaling one or more flags in the video bitstream toindicate the block partition candidate selected as the current blockpartition.
 5. The method of claim 1, further comprising signaling one ormore flags in the video bitstream to indicate a partition direction ofthe block partition candidate selected as the current block partition.6. An apparatus of depth-based block partitioning (DBBP) for multi-viewvideo coding or three-dimensional (3D) video coding, the apparatuscomprising one or more electronic circuits or processors arranged to:receive input data associated with a current texture block in adependent view; determine a corresponding depth block or a referencetexture block in a reference view for the current texture block; derivea representative value based on the corresponding depth block or thereference texture block; generate a current segmentation mask from thecorresponding depth block or the reference texture block; select acurrent block partition from block partition candidates, wherein therepresentative value is used for generating the segmentation mask orselecting the current block partition or both; and apply DBBP coding tothe current texture block according to the current segmentation maskgenerated and the current block partition selected, wherein therepresentative value is calculated from partial samples of thecorresponding depth block or the reference texture block, and thepartial samples correspond to only four corner samples of thecorresponding depth or the reference texture block, and the textureblock corresponds to a coding tree unit (CTU), a coding tree block(CTB), a coding unit (CU), or a prediction unit (PU).